1. Field of the Invention
The present invention generally relates to enclosures for the packaging of items and, more particularly, to packaging structures for isolating contamination sensitive items such as electronic components.
2. Description of the Prior Art
For many years, packaging has been an integral part of the transportation and delivery of products to users. One principal function of packaging for these purposes has been to provide ease of handling and space efficient storage of the product, prior to use. This may include packaging features which facilitate display of the product by dealers or information which is helpful in the selection and use of the product.
A further and often more important function of such packaging is the protection of the product from the time of production or manufacture until the time of use. Such protection has become particularly critical for electronic circuit components which are often subject to damage from a wide range of environmental conditions. Such conditions include, but are not limited to, accelerations during handling, such as impacts against surfaces, vibration, static electricity and contamination by vapors and particles and tampering.
To protect such devices, numerous containers have been designed and used in the past. Insertion of the pins of integrated circuit devices into a conductive foam which is supported by the package has been used to protect against static electricity and, to some extent, accelerations and vibration. However, this feature of some packaging does nothing to protect against contamination or tampering (e.g. removal and replacement of the device in the protective foam under conditions where damage could occur).
Other package features directed to prevention of contamination and tampering have included so-called bubble wraps where the device is placed in a recess formed in a plastic sheet and the recess sealed with cardboard, foil or the like. While such sealing of the recesses provides some protection against contamination and tampering (since the packaging cannot be opened without producing visible evidence thereof) provision of protection against vibration and impact accelerations is difficult since the item is usually only loosely enclosed within the packaging. Further, control of the atmosphere during and after packaging is difficult, especially since most plastics exhibit outgassing of vapors after manufacture or other processing. The bubble wrap form of packaging is also somewhat fragile and may easily sustain damage which would allow contamination by external ambient gases and particles without such damage being evident.
A variation of the bubble wrap form of packaging has been the so-called shrink wrap package. This type of package is formed by applying a vacuum through a backing sheet, usually of cardboard, to deform a plastic membrane around the item. This form of packaging is perhaps even more tamper resistant than bubble wrap packaging and offers some improvement of protection against vibration and impacts since the item is held tightly against the backing material. Some contamination resistance can be provided by sealing the backing sheet. However, since the plastic is formed tightly over the device, there can be no assurance that the plastic sheet will remain entirely intact during the packaging process. Further, the shrink wrap form of packaging has had little application to sensitive electronics products since the thermal and mechanical stresses, both from the deformation of the plastic sheet and the vacuum applied, can damage the product packaged. The product may also be damaged during removal from the packaging or may be affected by bits of the plastic film adhering to the product.
The above forms of packaging, therefore, do not simultaneously provide protection from even the most major environmental factors which could damage delicate electronic circuit components. While the above-discussed packaging techniques are relatively inexpensive and are only used a single time, they cannot provide the combination of features required for protection of such electronics components.
More expensive, reusable packaging, however, is usually of a more robust construction and is therefore less likely to be resistant to tampering or to show physical evidence that tampering has occurred. Moreover, the possibility of reuse introduces further problems of cleaning of the packaging between uses. Further, multiple uses implies the possibility of damage or wear which would shorten the usable lifetime of the container and increase expense. Such damage or wear rendering a container or a part thereof unsuitable for further use may not be evident from simple inspection.
The provision of single-use seals in combination with multiple-use containers also does not provide a complete solution to current packaging requirements. Such seals represent an added expense and often do not provide a smooth interior of the container, which can also be a source of damage to electronic devices contained therein. Additionally, single use seals may also represent a source of contamination during opening of the container and, when placed in compression, do not result in closely controllable interior and/or exterior dimensions of the package.
Further, none of the above packaging techniques provides for maintaining clean conditions during removal of the product from the package when the exterior surface of the package may have become contaminated. This requirement has become more important during recent years with the increase of storage and transportation of intermediate products for electronic devices which must be maintained in a clean condition when removed from the packaging for further processing. Further, the maintenance of an adequately clean manufacturing environment has led to increased manipulation of the packaging and items contained therein by automated processing equipment. Therefore, isolation structures must be adapted to be manipulated by such equipment in addition to providing the required types of protection for the packaged items. This adaptation often requires both the packaging and the automated equipment to be specially modified and standardized, increasing costs and reducing the generality of application of the automated equipment.